| 摘要 |
PURPOSE: To obtain an extremely thick wide-flange steel excellent in strength, toughness and weldability by hot-rolling a slab whose chemical composition and C-equivalent are specified into the side-flange steel under specified conditions and, further, executing air cooling after light reduction. CONSTITUTION: A steel base stock which consists of, by weight, 0.05-0.15% C, <=0.10% Si, 1.00-1.80% Mn, 0.005-0.050% Al, 0.0020-0.0070% N, 0.005-0.040% Nb, further, one or more kinds of 0.005-0.020% Ti, 0.05-0.60% Cu, 0.05-0.60% Ni, 0.05-0.50% Cr, 0.02-0.30% Mo, 0.0010-0.0020% REM, 0.0002-0.0030% B, 0.0010-0.0100% Ca, 0.005-0.080% V and the balance Fe and whose C-equivalent which is expressed by the equation is <=40% is used. This slab is heated to 1200-1350 deg.C and hot-rolled into the wide-flange steel whose flanges are >=40mm thick. Further, light reduction of <=3%/pass is added at <=900 deg.C and hot working of >=20% in cumulative draft is executed. Next, wide-flange steel is air-cooled to the room temp. |
